4,6-dihydroxy-5,5-dinitro-2-(dinitromethylene)-2,5-dihydropyrimidine represented by the formula 2 is used as a precursor of 1,1-diamino-2,2-dinitroethylene, which is a type of explosives represented by the formula 3, and is synthesized by the nitration of 4,6-dihydroxy-2-methylpyrimidine represented by the formula 1.

Describing the process in more detail, 4,6-dihydroxy-2-methylpyrimidine represented by the formula 1 is nitrated to give 4,6-dihydroxy-5,5-dinitro-2-(dinitromethylene)-2,5-dihydropyrimidine(precursor) represented by the formula 2, and then the precursor is hydrolyzed to give 1,1-diamino-2,2-dinitroethylene represented by the formula 3.
The nitration process of the 4,6-dihydroxy-2-methylpyrimidine is generally carried out by refluxing with concentrated sulfuric acid and concentrated nitric acid, and the most widely used method is the one proposed by A. A. Astrat'ev in Russian Journal of Organic Chemistry, Vol. 37, No. 5, 2001, p 729-733. In this method, firstly, 4,6-dihydroxy-2-methylpyrimidine is dissolved in a concentrated sulfuric acid at 15-20° C., the resulting solution is cooled to 5-10° C., and then nitric acid anhydride is slowly added to the solution while controlling the temperature to synthesize 4,6-dihydroxy-5,5-dinitro-2-(dinitromethylene)-2,5-dihydropyrimidine, as shown in the Reaction Scheme 1. The yield is reported to be about 75%.

The conventional method as described above, however, has the disadvantage of generating excessive reaction heat in the process of adding nitric acid. In the process with the laboratory-scale of about 50 ml of reaction liquid, it is possible to collect reaction heat by setting the stirrer speed of above 500 rpm. In the process with scale of more than 1 L of reaction liquid, however, the time of adding nitric acid anhydride tends to become longer in order to control the temperature within a predetermined range due to the generation of an excessive heat of reaction, and there is a danger of explosion by the reaction heat when temperature control is not accurate enough.